Justin Bieber was still in elementary school when Justin Timberlake released the single "Cry Me a River," but the 17-year-old star is now old enough to tackle the lyrics himself.

Biebs performed his song "Favorite Girl" and then a rendition of Timberlake's track at reported girlfriend Selena Gomez's concert on Sunday, although it wasn't entirely clear why he opted to serenade Gomez's audience with a song about an unfaithful lover.

But despite what the single may signal, there appears to be nothing but love between the two. Bieber later tweeted his support for Gomez, who turned 19 last Friday, and added that he's ready to get back out on the road himself.

"Had a #greatnight and suprised the people. felt good to be on stage," he wrote. "More excited than ever to get back in the studio and make this #newalbum. miss the tour and want to give u all new music."